Positive Fusional Vergence Research Articles

A Novel Device for Vergence Exercises: Testing Automatic Dual Rotational Risley Prisms on Asymptomatic Adults and Patients with Convergence Insufficiency.

This study investigated the effects of automatic dual rotational Risley prisms (ADRRPs), a mobile phone application-operated device, on vergence abilities in young adults. Fifty-six participants aged 20-24 performed vergence exercises. The test group used prisms with power changes from 30Δ base-out to 10Δ base-in, while the control group used plano lenses for 10min. Ophthalmic examinations included lateral heterophoria, near point of convergence (NPC), vergence facility (VF), negative fusional vergence (NFV), and positive fusional vergence (PFV), all measured before and after the vergence exercises. Pre- and post-test results were analyzed using a paired sample ttest. Additionally, three cases with convergence insufficiency (CI) performed similar exercises for 12weeks. Participants were divided into the test group (n = 39; age 21.82 ± 1.10years) and control group (n = 17; age 20.53 ± 0.51years). In the test group, NPC improved from 6.11 ± 2.52cm to 5.77 ± 2.30cm (p = 0.023). VF increased from 13.75 ± 4.10cpm to 16.50 ± 4.42cpm (p = 0.007). PFV at 6m and 0.4m increased from 19.49 ± 6.77∆ to 22.19 ± 6.64∆ (p < 0.001) and 20.51 ± 7.05∆ to 22.69 ± 6.44∆ (p = 0.012), respectively. After 12weeks, convergence insufficiency symptom survey scores for cases with CI decreased significantly, with NPC improving from 7.0 to 0cm, 6.0 to 5.8cm, and 6.0 to 4.7cm. PFV increased from 10 to 25∆, 20 to 30∆, and 25 to 50∆. This preliminary study showed the effect of ADRRPs on improving vergence abilities. Further studies are needed to investigate the long-term sustainability and effects in a larger population of individuals with CI of this approach.

Convergence insufficiency prevalence in attention deficit and hyperactivity disorder children depends on the diagnosis criteria.

Attention deficit and hyperactivity disorder (ADHD) is a neurodevelopmental condition commonly seen in children and adolescents, characterised by an increase in distractibility or inattention. Several studies have noted a higher rate of visual problems in this group, especially convergence insufficiency (CI), but when using different diagnostic criteria. The aim of this study was to evaluate visual function in ADHD children and non-ADHD controls to compare the different signs for diagnosis of CI. In this prospective case-control study, a group of children aged 7-17 years, diagnosed with ADHD before the start of pharmacological treatment and matched for age and gender with non-ADHD controls were examined. Visual acuity (VA), objective and subjective refraction, accommodative amplitude and facility, heterophoria, positive and negative fusional vergences (PFV and NFV) and stereopsis were assessed. Sixty participants (30 ADHD and 30 non-ADHD controls) were evaluated. There was no significant difference between the two groups for VA, refraction and accommodative abilities. There were significant differences in PFV and NFV: PFV break/recovery values for the ADHD and control groups were 18.9/16.2∆ and 26.9/22.1∆, respectively. Respective values for NFV were 15.7/13∆ and 19.3/15.9∆. Using the three signs of receded near point of convergence (NPC), decreased PFV and exophoria 4∆ greater at near than distance, the prevalence of CI was equivalent for the ADHD and controls (p = 0.34) If only two signs were considered for the CI diagnosis, (i.e., receded NPC and decreased PFV), then prevalence was significantly greater for the ADHD group (p < 0.01). These results show a higher prevalence of binocular vision problems in the ADHD group. This suggests a relationship between vergence problems and ADHD, but the direction of this link remains unclear. Further studies with specific samples may be needed to understand fully the association between binocular vision disorders and ADHD.

One-year follow-up of clinical convergence measures in children enrolled in the Convergence Insufficiency Treatment Trial-Attention and Reading Trial.

To assess the long-term stability of clinical measures of convergence (near point of convergence [NPC] and positive fusional vergence [PFV]) in participants enrolled in the Convergence Insufficiency Treatment Trial-Attention and Reading Trial (CITT-ART) who received 16 weeks of office-based vergence/accommodative therapy. A total of 310 children, 9-14 years old, with symptomatic convergence insufficiency were enrolled in CITT-ART. Some 270 completed both their 16-week primary outcome visit followed by a 1-year follow-up visit. Of those 270, 181 (67%) were randomised to the vergence/accommodative therapy. Of the 181 in the vergence/accommodative group, 121 (67%) reported not receiving any additional treatment after the 16-week primary outcome visit. The mean change in NPC, PFV and percentages of children classified by the predetermined success criteria of convergence (normal NPC [<6 cm] and/or improved by ≥4 cm; normal PFV [passing Sheard's criterion and base-out break >15Δ] and/or improved by ≥10Δ) were compared at the 16-week primary outcome visit and 1 year later. Of the 121 who returned for their 1-year follow-up visit, there was no significant change in mean adjusted NPC (reduction of -0.2 cm; 95% CI: -1.0 to 0.5 cm) at 1 year. There was a statistically significant decrease in mean-adjusted PFV (-4.7∆; 95% CI: -6.5 to -2.8Δ) at 1 year. There were similar percentages of participants classified as 'normal' (p = 0.30), 'normal and/or improved' (p > 0.50) and 'normal and improved' (p > 0.14) based on NPC and PFV at the 1-year visit compared with the 16-week primary outcome visit. The improvements in NPC and PFV following 16 weeks of vergence/accommodative therapy (with no reported additional treatment thereafter) in children with symptomatic convergence insufficiency persisted 1-year post-treatment.

From convergence insufficiency to functional reorganization: Alongitudinal randomized controlled trial of treatment-induced connectivity plasticity.

Convergence Insufficiency (CI) is the most prevalent oculomotor dysfunction of binocular vision that negatively impacts quality of life when performing visual near tasks. Decreased resting-state functional connectivity (RSFC) is reported in the CI participants compared to binocularly normal control participants. Studies report that therapeutic interventions such as office-based vergence and accommodative therapy (OBVAT) can improve CI participants' clinical signs, visual symptoms, and task-related functional activity. However, longitudinal studies investigating the RSFC changes after such treatments in participants with CI have not been conducted. This study aimed to investigate the neural basis of OBVAT using RSFC in CI participants compared to the placebo treatment to understand how OBVAT improves visual function and symptoms. A total of 51 CI participants between 18 and 35 years of age were included in the study and randomly allocated to receive either 12 one-hour sessions of OBVAT or placebo treatment for 6 to 8 weeks (1 to 2 sessions per week). Resting-state functional magnetic resonance imaging and clinical assessments were evaluated at baseline and outcome for each treatment group. Region of interest (ROI) analysis was conducted in nine ROIs of the oculomotor vergence network, including the following: cerebellar vermis (CV), frontal eye fields (FEF), supplementary eye fields (SEF), parietal eye fields (PEF), and primary visual cortices (V1). Paired t-tests assessed RSFC changes in each group. A linear regression analysis was conducted for significant ROI pairs in the group-level analysis for correlations with clinical measures. Paired t-test results showed increased RSFC in 10 ROI pairs after the OBVAT but not placebo treatment (p < 0.05, false discovery rate corrected). These ROI pairs included the following: Left (L)-SEF-Right (R)-V1, L-SEF-CV, R-SEF-R-PEF, R-SEF-L-V1, R-SEF-R-V1, R-SEF-CV, R-PEF-CV, L-V1-CV, R-V1-CV, and L-V1-R-V1. Significant correlations were observed between the RSFC strength of the R-SEF-R-PEF ROI pair and the following clinical visual function parameters: positive fusional vergence and near point of convergence (p < 0.05). OBVAT, but not placebo treatment, increased the RSFC in the ROIs of the oculomotor vergence network, which was correlated with the improvements in the clinical measures of the CI participants.

Age-Matched Comparative Analysis of Binocular Vision Anomalies among Children with Dyslexia in Northern Nigeria.

Background: Dyslexia, a neurodevelopmental disorder affecting reading skills, poses significant challenges to children's academic performance and quality of life. Despite its rising prevalence and adverse effects, understanding of its relationship with vision anomalies remains limited, particularly in low-resource settings like Nigeria. This study aims to assess the prevalence of binocular vision anomalies (BVAs) among children with and without dyslexia in Kano, Nigeria. Methods: This is a hospital-based, cross-sectional, matched-paired, controlled study conducted at the Aminu Kano Teaching Hospital (AKTH) Eye Clinic in Northern Nigeria. The study included school children who visited the AKTH Eye Clinic from January 2018 to December 2022. Visual acuity tests, external eye examinations and accommodative, binocular vision and oculomotor skills tests were conducted. Descriptive statistics, independent t-tests, Mann-Whitney U tests and Fisher's exact tests were conducted, with a significance level set at p < 0.05. Results: Forty-four children aged 12 ± 2 years participated. Children with dyslexia reported higher rates of visual symptoms than those without dyslexia, Blurring vision, visual distortion and eye strain were the most prevalent (p < 0.05) BV symptoms. Accommodative insufficiency), was the most common visual abnormality, and was significantly higher in children with dyslexia than those without dyslexia (45.5% vs. 18.2%). However, other visual anomalies showed no significant difference between groups. There was a high prevalence of binocular vision anomalies in both groups. Binocular test findings showed dyslexic children had significantly lower distance positive fusional vergence recovery values (p = 0.005). All cases of convergence insufficiency alone were found in the non-dyslexic group. Conclusions: The study found that children with dyslexia residing in Northern Nigeria demonstrated higher rates of visual symptoms, more accommodative insufficiency and lower distance positive fusional vergence recovery values compared to their non-dyslexic counterparts.

Comparative Effectiveness of different therapies for Convergence Insufficiency

Purpose: This study aimed to determine the effectiveness of different treatment options such as brock string, dot card, jump convergence and pencil push-up exercises for convergence insufficiency (CI). Methodology: After ethical approval, this quasi experimental study was conducted at District Head Quarter (DHQ) Bhakkar, Thel University Bhakkar, schools and collages of Bhakkar and district Layyah by selecting 140 patients presenting with symptomatic convergence insufficiency through non-probability convenient sampling. After informed consent, Positive Fusional Vergence (PFV), CI Symptom Survey (CISS) and near point of convergence (NPC) were measured. Then randomly divide into four groups of 35 patients by non-probability purposive sampling. Each group received one of the chosen therapy for 3 consecutive months. All patients were examined and self-structure proforma was filled as baseline data on each follow-up of therapy. Data was analyzed by IBM SPSS version 23. Results: After completion of three month of treatment, near point of convergence improved from mean 13.343 ±.219 to 8.757±.194; CI 95%: p&lt;0.001 respectively in brock string, mean 13.486 ±.197 to 7.729 ±.169; CI 95%: p&lt;0.001 in dot card exercise, in jump convergence mean 13.614 ±.214 to 9.057, ±.170; CI 95%: p&lt;0.001 improvement of NPC occur and in pencil push-up 13.243 ±.208 to 8.329 ±.143; CI 95%: p&lt;0.001. Conclusion: The dot card is most effective treatment to perform at home for CI, effective for achieving clinically significant improvements in signs and symptoms associated with CI in young adults.

Evaluation of convergence, accommodation and fusional vergence in pre-presbyopes with asthenopia

Background: Pre-presbyopes may suffer from ocular symptoms such as asthenopia of near work.Aim: This study aimed to evaluate near points of convergence, amplitudes of accommodation, and fusional vergence among pre-presbyopes with asthenopia symptoms.Setting: The study was conducted at El-Walidain Eye Hospital, Khartoum, Sudan in 2022.Methods: The study was a hospital-based prospective, including 107 pre-presbyopes aged 35–40 years who complained of asthenopia symptoms. Clinical examinations included an assessment of amplitude of accommodation, near point of convergence and fusional vergence.Results: The findings showed receded in near points of convergence and a decrease in the accommodation was highly significantly associated with increased age among emerging presbyopes with asthenopia symptoms (p = 0.0001). Conversely, positive and negative fusional vergence amplitudes were not significantly correlated with age with p = 0.109 and p = 0.355, respectively. Positive and negative fusional amplitudes were not significantly different between males and females (p ˃ 0.05). Esophoria was more common in pre-presbyopia 62 (57.4%) and exophoria 45 (43.6) with p = 0.503.Conclusion: The pre-presbyopes presented with low accommodation amplitude and receded near point of convergence, but without significant changes in positive and negative fusional vergence amplitudes.Contribution: This study added by demonstrating how early presbyopia altered accommodation amplitude and near point of convergence significantly while having no significant impact on amplitudes of positive and negative fusional vergence.

Comparison of Visual Symptom Frequency and Occupational Issues Between Patients With and Without Concussion.

Occupational therapy practitioners' knowledge of and advocacy for clients with visual symptoms postconcussion can have a considerable impact on recovery. To compare the frequency of vision symptoms and occupational performance deficits in a sample of participants with and without concussion. Cross-sectional study. Sports medicine clinic. Adolescents and adults with concussion (n = 20) and musculoskeletal injuries (n = 19). Measures included monocular amplitude of accommodation, near point of convergence, Binocular Vision Assessment (BVA) computerized screening for phoria, BVA computerized screening for fusional vergence, the Developmental Eye Movement Test, the Canadian Occupational Performance Measure, and the Convergence Insufficiency Symptom Survey-Concussion Version (CISS-CON). We found significant differences between participants with and without concussion using the CISS-CON (p = .001), positive fusional vergence (p = .02), and near point of convergence (p = .02). Participants with concussion scoring above cutoffs on multiple measures reported poorer performance (p = .005) and satisfaction (p = .004) with valued occupations. Concussion has a detrimental effect on vision and occupation, and occupational therapy practitioners are well-positioned to assess and address issues arising from this relationship. Plain-Language Summary: Vision symptoms commonly experienced after a concussion are associated with reduced occupational performance and satisfaction and can have a considerable impact on recovery. Occupational therapy assessment for clients with concussion should include screening for vision difficulties.

Comparison of vergence mechanisms between university students with good and poor sleep quality.

To compare the vergence mechanisms between good and poor sleepers in university students. A total of 64 university students were recruited in this study. The validated Malay version of Pittsburgh Sleep Quality Index questionnaire (PSQI-M) was used to measure the participants' sleep quality over the past month. Participants were categorized as good sleepers (n=32) and poor sleepers (n=32) based on the PSQI-M scores. Heterophoria and fusional vergences were measured at distance and near. Mann-Whitney U test was used to compare heterophoria, negative fusional vergence (NFV), and positive fusional vergence (PFV) at distance and near between good and poor sleepers. Spearman correlation analysis was used to study the relationship between PSQI-M score and PFV at distance. Both distance and near heterophorias were not significantly different between good and poor sleepers (P>0.05). There was a difference in distance PFV (P<0.05) between good and poor sleepers, but not in distance NFV, near NFV, and near PFV (P>0.05). Distance PFV was negatively correlated with PSQI-M score (rs=-0.33, P<0.05). University students with poor sleep quality demonstrates a reduced ability to maintain fusion with increasing convergence demand at distance. Sleep quality assessment during binocular vision examination in university students is recommended.

Comparison of Near Point of Accommodation and Near Point of Convergence with Positive Fusional Vergence among Young Adults, Bengaluru

Background: When encountered with mass screening and increased walk-in patients in outpatient departments (OPD), evaluating complete binocular vision assessment becomes time-consuming. Consequently, there is a need to streamline the testing process. This study also aims to explore if there are any correlations between Near Point of Accommodation (NPA) and Near Point of Convergence (NPC) with Positive Fusional Vergence (PFV). Methodology: A retrospective study was carried out at Sankara Eye Hospital in Bangalore. Data from patients aged 18 to 35, who underwent binocular vision assessment between 2016 and 2020, were included. Out of 101,896 patients who visited the hospital during this period, 3,449 attended the vision therapy clinic. Among them, 1708 patients met the criteria for inclusion, while 1,741 were excluded. Results: Out of 1708 subjects, 759 are females and 949 are males. The relationship between Near Point of Accommodation (NPA), Near Point of Convergence (NPC), and Positive Fusional Vergence (PFV) blur and break values were analysed. A positive correlation was observed between NPA and PFV blur (Spearman's rho = 0.069, p=0.004) and a negative correlation between NPC and PFV break (Spearman's rho = -0.370, p&lt;0.001). There was a significant difference between NPA and PFV blur, as well as NPC and PFV break (p=0.000), emphasizing the importance of incorporating all three tests in a binocular vision assessment. Conclusion: These results emphasize the necessity for complete binocular vision assessment to effectively diagnose and manage binocular vision anomalies. By accounting for the various parameters involved in this investigation, clinicians can enhance the precision and quality of their assessments and plan for appropriate treatment strategies for patients with binocular vision anomalies.

Heterophoria, fusional vergence, and near point of convergence in Sudanese hospital-based population

Background: Fusional vergence amplitude is the amount of convergence and divergence that can be induced before fusion is lost and fusional vergence amplitude controls heterophoria.Aim: This study aimed to investigate the relationship between near heterophoria, near fusional vergence (NFV), and near point of convergence (NPC).Setting: Al-Neelain Eye Hospital Khartoum, Sudan.Methods: A hospital-based prospective study from February to October 2019, included 230 patients with age range of 15–30 years and mean age and standard deviation of 19.46 ± 3.33 years. The alternate cover test with prism was used to measure near heterophoria and a prism bar was used to measure quantity of fusional vergence. All measurements were taken at near heterophoria (0.33 m). Then the associations between near heterophoria, NFV and NPC were assessed.Results: The most common heterophoria at near among the participants was exophoria: 200 (87.0%). Reported complaints of asthenopia were commonly found among these exophoric patients: 106 (86.9%) (P = 0.735). Positive fusional vergence (PFV) to the break point varied according to the forms of heterophoria (P = 0.003). Esophoria had a higher PFV to break point than exophoria (30.83 ± 8.79Δ compared to 25.59 ± 10.07Δ). Negative fusional vergence at the break and recovery points were higher among those with exophoria and lower in esophoria (P ˃ 0.05). The NPC differed by the type of heterophoria (P = 0.01), with exophoria and slightly receded NPC (8.38 cm ± 3.33 cm) than for participants with esophoria (6.77 cm ± 1.52 cm).Conclusions: Exophoria was the most common type of near heterophoria, with asthenopia being the most reported complaint. Esophoria was found to be strongly associated with high PFV. Exophoria, on the contrary, is related to significant high NFV at the blur, beak, and recovery point. The NPC differed significantly by the type of near heterophoria, with exophoria having more receded NPC compared to those with esophoria.Contribution: This study provides information on the commonest type of near heterophorias among a sample of Sudanese adolescents and young adults, namely exophoria. Near point of convergence and NFV at break and recovery points were significantly different according to forms of near heterophoria.

Effectiveness of treatment for concussion-related convergence insufficiency: The CONCUSS study protocol for a randomized clinical trial.

To describe CONCUSS, a randomized clinical trial (RCT) designed to compare the following: the effectiveness of immediate office-based vergence/accommodative therapy with movement (OBVAM) to delayed OBVAM as treatments for concussion-related convergence insufficiency (CONC-CI) to understand the impact of time (watchful waiting), the effect of OBVAM dosage (12 versus 16 therapy sessions), and to investigate the underlying neuro-mechanisms of OBVAM on CONC-CI participants. CONCUSS is an RCT indexed on https://clinicaltrials.gov/study/NCT05262361 enrolling 100 participants aged 11-25 years with medically diagnosed concussion, persistent post-concussive symptoms 4-24 weeks post-injury, and symptomatic convergence insufficiency. Participants will receive standard concussion care and will be randomized to either immediate OBVAM or delayed (by six weeks) OBVAM. At the Outcome 1 examination (week 7), clinical assessments of success as determined by changes in the near point of convergence (NPC), positive fusional vergence (PFV), and symptoms will be compared between the two treatment groups. After the Outcome 1 visit, those in the delayed group receive 16 visits of OBVAM, while those in the immediate OBVAM group receive four more therapy visits. Outcome 2 assessment will be used to compare both groups after participants receive 16 sessions of OBVAM. The primary measure is the between-group differences of the composite change in the NPC and PFV at the Outcome 1 visit. Secondary outcome measures include individual clinical measures, objective eye-tracking parameters, and functional brain imaging. Major features of the study design include formal definitions of conditions and outcomes, standardized diagnostic and treatment protocols, a delayed treatment arm, masked outcome examinations, and the incorporation of objective eye movement recording and brain imaging as outcome measures. CONCUSS will establish best practices in the clinical care of CONC-CI. The objective eye movement and brain imaging, correlated with the clinical signs and symptoms, will determine the neuro-mechanisms of OBVAM on CONC-CI.

Digital Challenges: Investigating Computer Vision Syndrome in Thai Esports Through a Case-Control Approach.

To determine the factors associated with eyestrain in esports athletes in Bangkok compared with controls. A cross-sectional descriptive study was conducted between April and June 2023, involving 160 male participants (aged 20-35 years) who used digital devices, consisting of esports athletes and a control group. Data were collected using a general information questionnaire, Computer Vision Syndrome Questionnaire (CVS-Q), and Depression anxiety stress scale-21 (DASS-21). Ophthalmic instruments were used for the eye examinations by an optometrist. Seventy-six esports athletes showed significantly lower visual performance than controls in logMAR visual acuity (p < 0.020), phoria (p < 0.001), negative fusional vergence (blur, break, and recovery) (p < 0.012, p < 0.004 and p < 0.039), positive fusional vergence (blur, break, and recovery) (p < 0.005, p < 0.001 and p < 0.005), monocular estimation method (p < 0.001), monocular and binocular accommodative facility (p < 0.001), and vergence facility (p < 0.001). A study on risk factors for CVS found that esports athletes were significantly more likely to have CVS (p < 0.001). Work environments with high-intensity lighting significantly increase the risk of CVS compared to low-intensity lighting (p < 0.001). The use of a digital device for >4 h/day, having a history of alcohol consumption, and stress significantly increased the risk of CVS (p < 0.001, p < 0.023, p < 0.048). This study found that esports athletes experienced vision health problems, indicating the need to prevent eyestrain caused by the use of digital devices.

The Impact on Vergence Parameters After Smartphone Gaming.

To evaluate the impact of smartphone gaming on the vergence system of the eye. A 5-month (from March 2023 to August 2023) comparative and experimental research was conducted. Eighty-two participants with a mean age of 21.98 ± 2.26 years were present in the study. Prior to assessing accommodation and vergence system characteristics, participants underwent a comprehensive eye examination. The participants were asked to play a shooting game on a smartphone for 30 minutes at a 40 cm distance. Measurements of the vergence parameters were taken before and after the activity and afterwards were compared. Non-parametric tests were used to compare pre- and post-task measurements. The Wilcoxon signed-rank test was used to compare the variables: Negative fusional vergence (NFV), Positive fusional vergence (PFV), Near point of convergence (NPC), and Vergence Facility (VF), with the alpha error set at 5%. The mean age of the participants was 21.98 ± 2.26 years. Post-task, the vergence parameters: NPC (p < 0.001), NFV for near distance (p < 0.001), PFV for near distance (p < 0.001), and VF (p < 0.001) showed significant decrease in vergence parameters. The study shows smartphone gaming for 30 minutes affects the vergence system, leading to binocular vision anomalies in young individuals.

Latent Convergent Strabismus Clinical Features and Management in Sudanese Patients

Purpose: To describe the clinical features and management of latent convergent strabismus among Sudanese patients. Study Design: Descriptive observational study. Place and Duration of Study: Makkah Eye Complex, Khartoum, Sudan, from December 2018 to August 2020. Methods: The study included 137 patients, diagnosed with latent convergent strabismus (esophoria). Demographic data and ocular examination findings including visual acuity, refractive error, and degree of esophoria was collected. Esophoria was assessed by prism cover test (PCT) at near and distance. Results: Esophoria was more common among females (n = 107, 78.1%) and in age group 15 to 25 years. Headache was the most common complaint (n = 64, 46.7%). Most of the patients (n = 114, 83.2%) had 1 to 5 ∆ of esophoria with a mean of 4.17 ± 2.99∆. Majority of the patients (n = 132, 96.3%) had normal near point of convergence (NPC) 6.98 ± 3.10 cm. Positive fusional vergence (PFV) was high at 24.06 ± 9.01∆, whereas negative fusional vergence (NFV) was low at 5.0 ± 0.21∆D, P = 0.001. Majority of the patients (76.6%) responded well to the refractive correction, 11.7% patients to vision therapy and remaining 11.7% to both refractive correction and vision therapy. Correlation coefficients revealed that there was a positive correlation between, refraction, NPC, and PFV (P ˃ 0.05). Conclusion: Sophoria was more common among females and young adults. Most of the esophoric patients had uncorrected hyperopia, good PFV and relatively poor NFV amplitude. Early detection and management of young esophoric patients is essential to improve vision and binocular functions.

Altered Large-Scale Resting-State Functional Network Connectivity in Convergence Insufficiency Young Adults Compared With Binocularly Normal Controls.

To investigate the underlying resting-state functional connectivity (RSFC) of symptomatic convergence insufficiency (CI) compared with binocularly normal controls (BNC) using functional magnetic resonance imaging (fMRI) under The Convergence Insufficiency Neuro‑mechanism Adult Population Study (NCT03593031). A total of 101 participants were eligible for this study. After removing datasets with motion artifacts, 49 CI and 47 BNC resting-state functional magnetic resonance imaging datasets were analyzed. CI was diagnosed with the following signs: (1) receded near point of convergence of 6 cm or greater, (2) decreased positive fusional vergence of less than 15∆ or failing Sheard's criteria of twice the near phoria, (3) near phoria of at least 4∆ more exophoric compared with the distance phoria, and (4) symptoms using the Convergence Insufficiency Symptom Survey (score of ≥21). RSFC was assessed using a group-level independent components analysis and dual regression. A behavioral correlation analysis using linear regression method was performed between clinical measures and RSFC using the significant difference between the CI and BNC. On average, a decreased RSFC was observed within the frontoparietal network, default mode network and visual network in patients with CI, compared with the participants with BNC (P < 0.05, corrected for multiple comparisons). The default mode network RSFC strength was significantly correlated with the PFV, near point of convergence, and difference between the horizontal phoria at near compared with far (P < 0.05). Results support altered RSFC in patients with CI compared with participants with BNC and suggest that these differences in underlying neurophysiology may in part be in connection with the differences in optometric visual function used to diagnose CI.

Binocular vision measurements with a new online digital platform: comparison with conventional clinical measures

ABSTRACT Clinical relevance New digital systems are being developed for evaluating different aspects of the visual function, such as binocularity, and it is important to know their real performance in clinical practice in order to use them appropriately. Background The aim was to compare binocular vision measures obtained with an online digital platform with conventional measures using prisms and printed tests. Methods Prospective study enrolling 49 healthy patients (mean age: 35.5 ± 13.6 years). A complete visual examination was performed including measurement of near phoria (cover test), negative fusional vergence (NFV) and positive fusional vergence (PFV) ranges (prism bar), and stereopsis (24 patients Randot Stereo Test and 25 patients TNO Random Dot Test 19th edition). These same parameters were also measured with the Bynocs system (Kanohi Eye Pvt Ltd). Bland – Altman plots were used to analyse the agreement between methods. Results Digital measurement of near phoria was significantly lower than that obtained with the cover test, with a median difference (MD) of 4.71 (−0.07–20.07) prism dioptres (pd) (p < 0.001). No significant differences were found between Bynocs and prism bar methods in NFV break (MD 2.00, range −21–26 pd, p = 0.584) and recovery points (MD 0.00, range −16–24 pd, p = .571). Near PFV were significantly lower with Bynocs (break: MD −9.00, range −38–12 pd; recovery: MD −14.00, range −43–20 pd; p < 0.001). Bynocs stereoacuity threshold was significantly lower than that obtained with TNO (p = 0.004), but significantly higher compared to Randot (p < 0.001). Large and clinically relevant confidence intervals for the comparison between digital and conventional measures were detected in Passing-Bablok analysis. Conclusions Digital measures of near phoria, NFV, PFV, and stereopsis with the Bynocs platform cannot be used interchangeably with conventional measures. The normal ranges of normality for this new tool are defined.

The Effect of Illumination on Positive Fusional Vergence.

Positive fusional vergence (PFV) is vital in maintaining fusion in critical and continuous near tasks such as reading or performing digital screen tasks. This study investigated how PFV changed under various lighting conditions. This cross-sectional study recruited 34 participants aged between 21 and 25 years, with best corrected visual acuity (BCVA) 0.0 logMAR and insignificant refractive error. Three different illuminations-low illumination (50 lux), medium lighting (100 lux), and high illumination (150 lux)-were used to examine the ocular parameters PFV (blur, break, and recovery points), contrast sensitivity and pupil diameter. Pupil diameter changed significantly in different room illuminations (p = 0.00). There was no significant difference in contrast sensitivity across the three levels of room illumination (p = 0.368). Mean PFV (SD) (blur) was 14.5 (2.5) in 50 lux, 10.2 (2.2) in 100 lux, and 8.2 (2.1) in 150 lux. Under 50, 100 and 150 lux, respectively, the mean PFV (SD) (break) values were 16.7 (2.4), 13.4 (1.8), and 10.8 (2.2), and the mean PFV (SD) (recovery) values were 13.3 (2.1), 10.7 (2.1), and 7.5 (2.7). With increased illumination levels, PFV blur, break, and recovery values were significantly lower (p < 0.001). PFV values were significantly higher in lower illumination. Clinicians should be aware that room illumination affected the PFV values measured.

Clinical features of Sudanese patients presenting with binocular vision anomalies: A hospital-based study.

Binocular vision anomalies are major causes of asthenopia symptoms, particularly among the younger population. This study aimed to report the clinical characteristics of Sudanese patients with binocular disorders who attended the orthoptic clinic at Al-Neelain Eye Hospital. In this retrospective hospital-based study, we analyzed data from 304 patients with binocular vision anomalies who visited the orthoptic clinic between October 2020 and June 2021. We collected information on demographics, symptoms, and eye tests such as visual acuity (VA), refractive error (RE), angle of deviation, and the assessment of fusional vergence. Our findings indicated that exophoria was the most common binocular vision anomaly, affecting 79.8% of males and 71.6% of females (p=0.731). Children between 6 and 17 years old showed the highest prevalence of exophoria (75.9%) (p=0.0001). Among patients with exophoria, 100% reported itching associated with tearing during fixation, while 89.5% experienced difficulty in fixation. Refractive error varied by the type of binocular vision disorders (p=0.0001), with higher hyperopia observed in cases of unilateral esotropia and alternate esotropia (+3.571±1.238 D and +3.023±1.553 D, respectively). Positive fusional vergence (PFV) differed by types of binocular vision disorders (p=0.0001) with high PFV in esophoria (18.063±6.848∆) compared to low PFV in exophoria (12.80±5.313∆). The most common types of exophoria were convergence weakness exophoria (45.39%), followed by convergence insufficiency (20.39%). The study concluded that exophoria was the most common binocular vision anomaly among Sudanese patients, with convergence weakness and convergence insufficiency being the predominant anomalies. Headache was commonly prevalent among patients with binocular vision problems. Higher hyperopia was found in esodeviation, while low PFV was associated with exodeviation.

Feasibility of measuring fusional vergence amplitudes objectively.

Two tests to measure fusional vergence amplitudes objectively were developed and validated against the two conventional clinical tests. Forty-nine adults participated in the study. Participants' negative (BI, base in) and positive (BO, base out) fusional vergence amplitudes at near were measured objectively in an haploscopic set-up by recording eye movements with an EyeLink 1000 Plus (SR Research). Stimulus disparity changed in steps or smoothly mimicking a prim bar and a Risley prism, respectively. Break and recovery points were determined offline using a custom Matlab algorithm for the analysis of eye movements. Fusional vergence amplitudes were also measured with two clinical tests using a Risley prism and a prism bar. A better agreement between tests was found for the measurement of BI than for BO fusional vergence amplitudes. The means ± SD of the differences between the BI break and recovery points measured with the two objective tests were -1.74 ± 3.35 PD and -1.97 ± 2.60 PD, respectively, which were comparable to those obtained for the subjective tests. For the BO break and recovery points, although the means of the differences between the two objective tests were small, high variability between subjects was found (0.31 ± 6.44 PD and -2.84 ± 7.01 PD, respectively). This study showed the feasibility to measure fusional vergence amplitudes objectively and overcome limitations of the conventional subjective tests. However, these tests cannot be used interchangeably due to their poor agreement.